1. Field of Invention
The field of invention relates generally to computer systems and, more specifically but not exclusively, relates to switching between a service virtual machine and a guest virtual machine in a virtual machine monitor environment.
2. Background Information
In a typical PC architecture, the initialization and configuration of the computer system by the Basic Input/Output System (BIOS) is commonly referred to as the pre-boot phase. It is generally defined as the firmware that runs between the processor reset and the first instruction of the Operating System (OS) loader. At the start of a pre-boot, it is up to the code in the firmware to initialize the system to the point that an operating system loaded off of media, such as a hard disk, can take over. The start of the OS load begins the period commonly referred to as OS runtime. During OS runtime, the firmware acts as an interface between software and hardware components of a computer system. As computer systems have become more sophisticated, the operational environment between the application and OS levels and the hardware level is generally referred to as the firmware or the firmware environment.
In today's servers, the system architecture allows for a bi-modal server management. Generally, a server has a server management OS and a guest operating system (OS). The management OS includes diagnostic tools and utilities to service the guest operating system and the server environment. The guest OS operates as a conventional operating system. Usually, the system first boots the management OS from the system management partition, and then the system must be rebooted in order to run the guest OS.
However, rebooting into the guest OS results in the loss of all state information from the management OS. Also, if there is a system failure while running in the guest OS, the machine must be rebooted back into the management OS for diagnosis. This reboot results in the loss of key state information that could be analyzed to discover system problems.
Also, some guest OS faults are so severe that the guest OS cannot take a snapshot of its own system state or perform an error dump to a storage device. Thus, vital information for system managers will be lost because the only solution is to reboot the system. Further, if the same error repeats itself, for example due to a mis-configured software patch, the system may continually crash without a scheme to diagnose the error.